Study On Composite Photodetector Based On Two-dimensional Bismuth Oxyselenide And Plasmonic Structure

In the information age,photodetectors have important applications in optical communication,imaging,laser radar and numerous other fields.Due to the rapid development of these fields,photodetectors oriented to the near-infrared band tend to achieve room temperature operation,fast response and high sensitivity simultaneously.And the future development of semiconductor technology pursues high integration and device miniaturization.Therefore,two-dimensional materials exhibit great potential in photodetectors by their strong light-matter interaction,high carrier mobility and easy integration.Bi₂O₂Se has broad application prospects in two-dimensional material photodetectors because of its tunable band gap controlled with thickness,ultra-high carrier mobility at room temperature and stability in high heat and humidity.However,the ultra-thin atomic thickness of the two-dimensional material limits the intrinsic absorption capacity of the material to light.Meanwhile,the near-infrared photoresponse of the intrinsic Bi₂O₂Se photodetector decline rapidly compared with that of the visible range.In order to improve the detection performance of Bi₂O₂Se devices in the near-infrared band,we import the semiconductor plasmonic Mo O_3-xarray to prepare the Mo O_3-x/Bi₂O₂Se plasmonic composite photodetector.The local light field enhancement caused by surface plasmon resonance is used to improve the light utilization efficiency of two-dimensional Bi₂O₂Se.Meanwhile,plasmon-introduced hot electrons inject Bi₂O₂Se with the transfer speed of femtosecond.Moreover,the long Bi₂O₂Se carrier lifetime can keep the injected hot electrons in high-energy excited state for ballistic transport,and inhibit the in-band cooling,defect binding and carrier recombination,thus successfully enhancing the weak light detection ability of Bi₂O₂Se in the near-infrared band.This paper mainly focuses on three aspects of research,the research results are as follows:1.Bi₂O₂Se flakes suitable for photodetectors are grown by chemical vapor deposition.Since the thickness of two-dimensional Bi₂O₂Se affects the Hall mobility and dark current of its FET,it is necessary to regulate the experimental parameters that affect the size and thickness of Bi₂O₂Se,such as growth temperature,reaction time and carrier gas flow rate,to achieve the controlled growth of Bi₂O₂Se flakes.The experimental results show that temperature affects the dominant growth mode of Bi₂O₂Se.At low temperature,materials tend to grow along the substrate with low binding energy.At high temperature,transverse growth of the material is dominant in the substrate plane.Meanwhile,the material will not always grow with the increase of reaction time,there is an optimal growth time parameter.In addition,the carrier gas flow rate affects the deposition rate and size of materials.When the growth temperature is700℃,the reaction time is 10 min,and the flow rate of carrying gas is 150 sccm,the high quality Bi₂O₂Se with uniform thickness and smooth surface can be obtained.2.Two-dimensional Bi₂O₂Se flakes obtained under the optimum growth conditions are selected.Raman,SEM,AFM,EDS and other characterization methods showed that Bi₂O₂Se flakes has smooth surface,uniform element distribution and high crystallinity.The Raman characteristic peak A_1gof Bi₂O₂Se is located at 157.8 cm^-1,and has strong interaction with visible light.The size distribution of Bi₂O₂Se is 30μm-40μm and the thickness of Bi₂O₂Se is about 12 nm.3.Study on photodetector performance of two-dimensional Bi₂O₂Se plasmonic composite structure.Intrinsic Bi₂O₂Se and Mo O_3-x/Bi₂O₂Se composite photodetectors are obtained by wet transfer and micro-nano device processing.The experimental results exhibit that the photoresponse speed of Bi₂O₂Se photodetector is 358 ns at 400 nm and 7.51×10⁴A/W at 700nm.After adding the Mo O_3-xstructure,the photoresponse of the Mo O_3-x/Bi₂O₂Se device in the near-infrared band（1000 nm-1550 nm）is improved.The responsivity of the device at 1310nm and 1550 nm is～24 A/W and～1 A/W,respectively,which is more than 10 times stronger than that of the intrinsic Bi₂O₂Se device.The specific detectivity and external quantum efficiency at 1310 nm reach 6.4×10⁹Jones and 2.27×10³%,respectively,and the response timeτ_riseis 10 ms.The specific detection rate at 1550 nm is 2.1×10⁸Jones,the EQE reaches80%,and theτ_riseis 24 ms.The above-mentioned results prove that importing the Mo O_3-xstructure into two-dimensional Bi₂O₂Se can enhance the weak light detection ability of the device in the near-infrared band,and has a broad application prospect in photodetector with high sensitivity,low power consumption and fast response.